The invention relates to a preliminary size reduction device for a ball mill or an agitator ball mill and a ball mill with a preliminary size reduction device. The ball mill is a device for the coarse, fine and extremely fine size reduction or homogenisation of grinding stock. It comprises a grinding chamber which is caused to rotate and in which grinding stock is size-reduced by grinding bodies. Ball mills usually comprise an approximately circular-cylindrical grinding container mounted horizontally rotatable. The mills are filled through a central opening at one of the end walls, the so-called grinding stock inlet. The output is dependent on the design and takes place for example via slots in the grinding chamber wall at the end of the mill, wherein the grinding bodies are held back by a separating device.
A special form of the ball mill is the agitator ball mill. Agitator ball mills comprise a vertically or horizontally disposed, usually approximately cylindrical grinding container, which is filled 70-90% with grinding bodies. The grinding chamber is usually mounted stationary, non-rotating, in the case of agitator ball mills. An agitator with suitable agitator elements provides for the intensive motion of the grinding bodies. The grinding stock suspension is continuously pumped through the grinding chamber. The suspended solids are size-reduced or dispersed by impact or shearing forces between the grinding bodies. The separation of grinding stock and grinding bodies takes place by means of a suitable separating device at the exit from the mill.
Document DD 217434 B1 describes a vertically disposed agitator ball mill, which comprises in the upper inlet region a preliminary size reduction device connected to the agitator shaft. Said preliminary size reduction device comprises a crushing cone, which is disposed rotationally fixed on the agitator shaft, and a crushing ring fixed to the grinding container. The grinding stock is introduced into the crushing gap between the crushing cone and the crushing ring and thereby undergoes preliminary size reduction, before it falls into the grinding container, in which it is worked further by the agitator shaft and the grinding bodies.
Document DE 102008058585 A1 discloses an agitator ball mill with a horizontally disposed grinding chamber and an agitator shaft, wherein a preliminary size reduction device is provided between the grinding stock inlet and the grinding chamber, said preliminary size reduction device comprising a gap protection to the grinding chamber. This thus prevents grinding bodies from being able to flow back and get into the preliminary size reduction device.
EP 1980323 B1 describes a cutting system with a cutting rotor, which comprises rotor bars, at the outwardly facing surfaces whereof rotor cutting plates with cutting edges are fixed. A stator ring with an annular base and stator bars is disposed around the cutting rotor. The stator bars each comprise an inwardly facing stator recess with a stator cutting plate. The stator cutting plates are each disposed and fixed such that they each lie opposite the rotor cutting plates.
The problem underlying the invention is to improve the preliminary size reduction of solid constituents of grinding stock, in particular to make available a preliminary size reduction device, wherein the problem of jamming of coarse particles and/or impurities is reduced or minimised.
The above problems are solved by a preliminary size reduction device for ball mills and/or agitator ball mills and a ball mill with a preliminary size reduction device.